Study of the heavy flavor content of jets produced in association with W bosons in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.8 TeV

TL;DR

This study probes heavy-flavor content in W+jets at the Tevatron using SECVTX displaced-vertex tagging and SLT soft-lepton tagging to identify b- and c-hadron jets. By comparing observed tag rates across jet multiplicities to SM predictions (including tt̄, Wg, and gluon-splitting components) and employing MC tuning, the authors generally find agreement, but uncover a notable excess of events where a jet carries both a secondary vertex and a soft lepton (a superjet) in W+2,3 jet final states. Kinematic analyses and cross-checks suggest that this excess is difficult to reconcile with the SM within current statistics and despite extensive detector and background checks, leaving open questions about possible new physics or subtle modeling deficiencies. The results motivate larger data samples (Run II) to further investigate this anomaly and refine heavy-flavor modeling in W+jets processes.

Abstract

We present a detailed examination of the heavy flavor content of the $W $ + jet data sample collected with the CDF detector during the 1992-1995 collider run at the Fermilab Tevatron. Jets containing heavy flavor quarks are selected via the identification of secondary vertices or semileptonic decays of $b$ and $c$ quarks. There is generally good agreement between the rates of secondary vertices and soft leptons in the data and in the standard model simulation including single and pair production of top quarks. An exception is the number of events in which a single jet has both a soft lepton and a secondary vertex tag. In $W +$ 2,3 jet data, we find 13 such events where we expected 4.4 $\pm$ 0.6 events. The kinematic properties of this small sample of events are statistically difficult to reconcile with the simulation of standard model processes.

Figures (23)

• Figure 1: Distributions of the transverse energy of the primary lepton for the data ($\bullet$) are compared to the SM prediction (shaded histograms). The dotted histograms show the SM simulation normalized to the data. The probability distribution of the K-S distance $\delta$ is calculated with Monte Carlo pseudo-experiments (see text). The vertical line indicates the observed distance $\delta^{0}$ between the cumulative distributions of the data and the simulation. The integral of the shaded area represents the probability $P$ of measuring a K-S distance no smaller than $\delta^{0}$.
• Figure 2: Distribution of the pseudo-rapidity of the primary lepton in events with a superjet and in the complementary sample.
• Figure 3: Distribution of the transverse energy of the superjet in events with a superjet and in the complementary sample.
• Figure 4: Distribution of the pseudo-rapidity of the superjet in events with a superjet and in the complementary sample.
• Figure 5: Distribution of the transverse energy of all $b$-jets in events with a superjet and in the complementary sample.